Friday, 20 September 2013

MFX's Deck Girders

Deck Girder Construction and Modifications.
The 24' Deck Girders Bridges are manufactured by Waratah Models using all etch brass construction making them ideal to integrate MFxs. The notes below cover some tips for assembly and the modifications to integrate the MFxs

Parts were separated from the frets using a pair of 100 mm pair of stainless steel scissors. These are excellent for trimming off the fine attachment that bind the parts into the fret. They however only last 3 or 4 kits before loosing the edge so purchase a few as they are cheap.

The girders will require a timber jig to solder the top and bottom flanges in there correct relationship to the web. The jigs packers were laminated from 0.5 mm scale lumber to center the flange on the web. The assembly was soldered using 0.5 mm rosin cored electrical solder and paste flux using a temperature controlled iron set at 400 deg C with a chisel tip. Check that the web is located about the flange center-line before soldering the rivet strips.

Timber Jig with flanges installed - Finished girder above

The construction of the kit was altered by removing the internal cross bracing and replacing it with a folded brass channel 45 mm wide x 5 mm high x 0.4 mm thick x 150 mm long.

Tip: When folding metal you gain a gauge at each fold line [material thickness]-to obtain a finished width of 45 mm two metal thickness are deducted to locate the fold lines. The girder sides a packed with tissue paper saturated with water and applied to absorb the heat required to fit the channel.

The top side of the channels supported in its correct position using to strips of 5 mm square lumber - this dimension is not critical. Low temperature [280 deg C] solder is applied at three points along the flange of the channel with heat applied using a propane torch. Start at one end and allow the assembly to cool and move to the opposite end - repeat at the center.

Clean check alignment and repeat for the opposite side


All etches for vertical angles are folded using a "Hold and Fold" from the Small Shop as hand folding proved impractical. After folding the vertical flange there is a notch formed at the end of the angle to fit over the rivet strip located at the base of the flanges. If it is not correctly formed remove a metal thickness at both ends - see photo below. 

Fit to the instructions provided by the manufacturer and solder using 0.5 mm rosin core solder and a propane torch.

Solder located against vertical ready for soldering
Only the front verticals were installed to allow the channel spreader to be fitted

Tip: Apply the heat gently to melt the flux and then move in closer to quickly to build temperature at the center and melt the solder. The heat is initially applied at the center of the vertical on the opposite side to the solder and when at the solder appear to distort move the flame to the other side. Repeat for each verticals allowing most of the heat to dissipate between applications.

The angle spreaders and associated bracing are installed across the girders top and bottom.

The sound effects are created by a ModelFXs Sound-Byte Player with the bridge rumble file using a exciter speaker mounted about the bridge bent spreader centers.

The exciter speakers were purchased from Parts Express and fixed to the inside face of the channel using the self adhesive mounting pad. A exciter's frequency response and sensitivity are completely dependent on the exciter's designated surface. Thinner, smaller materials will tend to be louder and facilitate mid/tweeter response. Thicker, larger materials will be slightly quieter but result in a more full-range sound.

HiWave HIAX 19C01- 8 19 mm Metal Cup Exciter Specifications:Power handling: 3 watts RMS •Nominal impedance: 8 ohms • Mounting diameter at face: 22 mmBody diameter 40 mm(including terminals) x 13 mm H • Weight: 29 grams.

The ModelFXs Bridge sound file is as dimensionless [speed] as practical but still creates a fixed relationship to equipment crossing the bridge so a fixed speed restriction will be applied in that area of the layout.

Sound and Control Logic Overview
The player plays the sound on continuous loop with one of the speaker wired run through the normally open contact of a NCE Dual Relay. A BOD20 detects the presence of a train and triggers an output on a NCE Mini Panel with code associated with that output triggering an output on a NCE Switch 8 stationary decoder activating the coil on the Dual Relay connecting the speaker. This approach combined into the three bents using the same logic allows the sound to effectively follow a locomotive across each bents.

Air Movement
To create a sense of motion the air movement associated with trains crossing a bridge is to be simulated with a fan. The fan is used to push away mist at the base of the bridge which is created with a ultrasonic mist generators. These will be employed during the night to fill the creek bed with water mist for the early morning trains to run through.

Ultrasonic Mist Fogger 24v DC

Two axial 5V DC fan are fitted at the entrance's of the center bent and are coordinated by the locomotive using a pair of BOD20's located on the opposite rail to the sound triggers. The fans are mounted between the girders pointed too the creek bed and are controlled using two NCE D13SRJ functions with the firebox flicker effect assigned to the function to flicker the fan creating flukey air movement of the real world. The D13SRJ decoder are controlled by the code in a NCE Mini Panel associated with the triggering BOD20.

Fan 5v DC - 20 x 20 x 10 mm

Control Logic Overview
All electronics will be located in the module drawers fitted to the base of the module frames. This will allows repair and diagnostics to be achieved without removing models and electronic hardware from the layout. Full schematic and control logic will be found in the article on Spicers Creek Control Logic

Wrap up
MFxs cannot replicate real life as scaling effects are difficult to overcome but MFxs is an attempt to suspended the reality of a viewer and if that is achieved the goal has been achieved. Only time will tell if the result is success but for this builder simulation is the next frontier in all our hobbies involving modeling and motion and there has never been a better time to try.

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